It really depends on how you plan to cook them, i.e. on the grill over charcoal, steamed, boiled, baked, or broiled. I have cooked them both with the back of the shell cut from one end, to the other (kitchen shears work great for this, much easier than using a knife), and the same, but cutting the belly side. Use a spoon to separate the meat from the shell, letting it sit on top of the slit. If you desire, you can stuff the shell with a forcemeat of shredded crab, or minced shrimp. Rub the lobster meat, and stuffing with a compound butter flavored with a little Old Bay, and garlic, or just plain butter.
If cooking over charcoal, cook uncut shell side down, until the lobster meat just turns white, and loses its translucent look. The shell will turn red. Over-cooking will make it tough, chewy, and dry.
If cooking under the broiler, cook the forcemeat/stuffing, if using, separately. Place the lobster under the broiler, and cook again until the meat is white, and the shell turns red.
If steaming, bring the water to a rolling boil Place lobster tails into the steamer over medium heat. Cover, and steam for about 7 minutes. Check the lobster tails. If the meat is white, and the shell is red, they are done.
Some people boil their lobster tails. If this is done, you have to add enough salt to the water to make it taste like the sea. Otherwise, you lose a good bit of flavor. Boiling is quick, again only 7 minutes or so.
It's best not to rely on time, but rather to recognize what fully cooked lobster meat looks like, as cooking time will vary with the size of the lobster tails, and whether the tails are stuffed.
I food this video, and it's pretty informative. This guy is doing it right. Of course you can change up the flavors in your herbed butter: https://www.google.com/search?q=yout...z0PEPzoSRoA438
If you want to get fancy, for stuffed lobster, there is this:
I hope this answers your questions about cooking lobster tais.
Just remember, when in doubt, use an instant read thermometer, lookin for internal temp 0f 137, to 140' F, in thickes meat portion.
Seeeeya; Chief Longwind of the North